index.js

const Telegraf = require('telegraf')
const config = require('./config.json')

var photos = {}

const bot = new Telegraf(config.token)

bot.start((ctx) => {
  photos[ctx.from.id] = []
  return ctx.reply('Please, send me from 2 to 10 photos.\n'
      +'Send /done to create album or /cancel to abort operation')
})

bot.command('/cancel', (ctx) => photos[ctx.from.id] = [])

bot.command('/done', (ctx) => {
  if (photos[ctx.from.id].length < 2 || photos[ctx.from.id].length > 10) return
  done(ctx)
})

bot.on('photo', (ctx) => {
  const lastPhoto = ctx.message.photo.length - 1
  photos[ctx.from.id] = photos[ctx.from.id] || []
  photos[ctx.from.id].push({type: 'photo', media: ctx.message.photo[lastPhoto].file_id})
  if (photos[ctx.from.id].length >= 10) {
    done(ctx)
  }
})

function done(ctx) {
  ctx.replyWithMediaGroup(photos[ctx.from.id])
  photos[ctx.from.id] = []
}

bot.startPolling()